From what I've seen there are two narratives people point to as evidence of this being intentional, in one way or another:

- A new "pandemic" every six years (they count things like swine flu, so not quite pandemic)

- the seeming stupidity of taking a disease outbreak contained to one easy to quarantine place and putting those people on commercial airliners with minimal precautions, to quarantine them at their destination. I can practically hear the "I'm not trying to say they are trying to spread it, but if they did what would they do differently"

I don't have strong opinions on this, but those are the things I've seen on the interwebs